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Microinvasive Glaucoma Surgery (MIGS)

MIGS are relative new surgical procedures for the treatment of mild to moderate glaucoma. There are various types of procedures that fall into this less invasive method of treating glaucoma. There are 4 basic categories of treatments.

Increasing trabecular outflow

Suprachoroidal shunts

Reducing aqueous humor production

Subconjunctival filtration

Increasing trabecular outflow

These procedures are designed to increase outflow of fluid from the eye by treating the juxtacanalicular system and/or trabecular meshwork. The increased resistance of fluid flow out of the eye through the trabecular meshwork is felt to be the primary source for the development of open-angle glaucoma. The procedures are designed to either bypass or remove the trabecular meshwork and inner wall of Schlemm’s canal located behind the trabecular meshwork. The fluid can then pass through the collector channels in Schlemm’s canal to be removed from the eye. In patients with high episcleral venous pressure, these procedures may not be effective. Patients who have had retinal detachment procedures with a scleral buckle, Grave’s disease, and need very low eye pressures.

The iStent was FDA approved in 2012 for the treatment of mild to moderate open-angle glaucoma to be used during cataract surgery. The iStent was developed by Glaukos Corporation in Laguna Hills, California. iStent is the first-generation trabecular meshwork bypass device that directly connects the fluid in the anterior chamber into Schlemm’s canal. The iStent is heparin-coated and is a non-ferromagnetic titanium stent that is 1×0.3 mm in size.

The iStent is placed into Schlemm’s canal after the cataract surgery is completed. The eye is formed with viscoelastic to keep the eye formed during the procedure. A gonio prism is placed on the eye in order to visualize the trabecular meshwork. The iStent is on the tip of an inserter with a button release. Schlemm’s canal is penetrated and the stent is inserted in a sideways fashion.

Studies have shown that the iStent lowers the eye pressure by at least 20% in 66% of cases verses cataract surgery alone in 48%. Inserting more than 1 stent can lower the eye pressure further but is not approved in the United States at this time. There is chance that the stent could dislodge and many people have a small hemorrhage that resolves over a few days.

The Trabectome procedure was approved by the FDA in 2004. The Trabectome was developed by Neomedix in Tustin, California. The Trabectome performs a trabeculotomy using a handpiece that is a 19.5 gauge in diameter with an electrocautery connected to and irrigation and aspiration system connected to a control console. Using a Gonioscopy lens to view the trabecular meshwork, the instrument is passed along the trabecular meshwork. The device removes a strip of trabecular meshwork and inner wall of Schlemm’s canal. Approximately 120 degrees of trabecular meshwork is removed. This allows the fluid in the anterior chamber direct access to collector channels in Schlemm’s canal to be drained from the eye.

On an average, the Trabectome procedure lowers the eye pressure about 30% from the baseline eye pressure. There is some mild bleeding from Schlemm’s canal but this usually resolves within 1 week.

GATT is a minimally invasive ab interno trabeculotomy. There 2 incisions made through the cornea into the anterior chamber. Viscoelastic is injected into the anterior chamber to maintain the form of the eye during surgery. A small incision is made in the trabecular meshwork with a sharp blade. An illuminated microcatheter (iTrack-Ellex) is inserted into Schlemm’s canal. Using a microsurgical forcep, the catheter is passed all the way around the eye and the tip exits the opening in the trabecular meshwork. The catheter is grasped by the microsurgical forcep and the catheter cuts through the trabecular meshwork the total 360 degrees around the eye. A total trabeculotomy is performed.

GATT produces an approximately 30% reduction in the eye pressure. The most common complication is a hemorrhage inside the eye. This usually absorbs in a week or so.

The Kahook Dual Blade is used to remove a portion of the trabecular meshwork. The Kahook Dual Blade was designed to remove the trabecular meshwork in a more complete fashion compared to other techniques. Removing a wider band of tissue may decrease the eye’s ability to scar the meshwork closed. The Kahook Dual Blade procedure can be performed alone or during cataract surgery.

The anterior chamber is filled with viscoelastic to maintain the form of the eye. The patient’s head is rotated 30 to 40 degrees away from the eye surgeon. A gonio lens is placed on the eye to view the trabecular meshwork. The Kahook Dual Blade is inserted through the meshwork into Schlemm’s canal and advanced along the trabecular meshwork. The blade is rotated 180 degrees and inserted into the meshwork on the opposite side of the eye advanced back in the opposite direction to join the 2 incisions. This results in a free-floating piece of trabecular meshwork. Up to 180 degrees of trabecular meshwork may be removed. The piece and the viscoelastic are removed with irrigation and aspiration.

The average reduction in eye pressure is 30%. The most common complication as with these types of procedure is a hemorrhage that usually resolves in a week.

The Hydrus Microstent is an intracanalicular scaffold made by Ivantis for the treatment of open angle glaucoma. The Hydrus Microstent increases fluid outflow through the trabecular meshwork by serving as a scaffold for Schlemm’s canal. The Hydrus Microstent is made from a highly flexible biocompatible alloy of nickel and titanium 8mm in length. The 1mm inlet segment resides in the anterior chamber and the scaffold segment resides in Schlemm’s canal.

The results of the procedure show a 20% reduction in eye pressure after the surgery. As with other trabecular meshwork surgeries, hemorrhages did occur which resolved in a week or so. There was also some peripheral anterior synechiae formation which did not change the outcomes.

The Hydrus Microstent is unique in the ability to scaffold Schlemm’s canal for several clock hours inside the eye.

The TRAB 360 device is a disposable non-powered instrument used to perform an interno 360-degree trabeculotomy for the treatment of open angle glaucoma. The instrument is made by SightSciences.

The patients head is turned away from the surgeon. A gonioprism is placed on the eye for viewing the trabecular meshwork. A small incision is made if not performing the procedure during cataract surgery. The eye is filled with viscoelastic to keep the eye formed during the operation. The device is inserted into the eye and the tip of the TRAB 360 is used to make a small opening in the trabecular meshwork. The TRAB probe is inserted into Schlemm’s canal. The flexible nylon cannula is advanced 180 degrees. The TRAB 360 is pulled away from the meshwork and opens the 180 degrees of Schlemm’s canal. The probe is reinserted into Schlemm’s canal and the cannula is passed in the opposite 180 degrees. The probe is pulled away from Schlemm’s canal and the other 180 degrees of Schlemm’s canal is opened.

The results from this procedure show an approximately 35% decrease in eye pressure following the surgery. As with the other trabecular meshwork procedures, the most common complication was intraocular hemorrhage which usually resolves in a week or so.

ELT uses a 308 nm xenon chloride excimer laser to make openings in the trabecular meshwork. There are two devices currently available to perform ELT. AIDA; Glautec AG, Nuberg, Germany and AIDA; TUI-Laser, Munich, Germany make the devices.

A small temporal incision is made in the cornea and the eye is formed with viscoelastic. The laser probe is placed in the eye and passed across the anterior chamber. The probe is directly applied to the trabecular meshwork. The laser has a wavelength of 308 nm, a spot size of 200 microns, an energy setting of 1.2 mJ, and a duration of 80 ns. Usually 10 laser applications of the laser are applied to the nasal trabecular meshwork about 500 microns apart. There may be some minor bleeding from the trabecular meshwork but will resolve in a few days.

The results show that there is a reduction in eye pressure of approximately 30% and a reduction in the number of medications used by 30 to 40%.

Visco 360 is similar to TRAB 360 and is manufactured by SightSciences. It is the first non-implantable MIGS surgery device indicated for ab interno microcatherization and viscodilation of Schlemm’s canal in patients with open-angle glaucoma.

A small incision is made in the cornea temporally and the eye is formed with viscoelastic. The probe is placed in the anterior chamber and a small opening is made in the trabecular meshwork. The flexible nylon canula is passed around the eye and viscoelastic is injected into Schlemm’s canal as the canula is retracted back around Schlemm’s canal.

This device is still under investigation by the FDA and results are not available at this time.

Suprachoroidal shunts

The supraciliary space for fluid outflow has been used for the treatment of glaucoma for decades. There were many complications related to the older procedures using the supraciliary space. The newer procedures are having very good success.

The Cypass comes with a pre-loaded guide wire that is retractable. A 1.5 mm incision is made in the temporal cornea if not done during cataract surgery. Viscoelastic is used to keep the eye formed during the procedure. The Cypass is inserted into the supraciliary space between the ciliary body and sclera. The guide wire is removed.

The most common complication was bleeding in the eye which resolved over time. Peripheral anterior synechiae around the stent and postoperative inflammation occasionally occurred. There was a nearly 35% reduction in eye pressure following the procedure.

The Cypass Micro-stent is a suprachoroidal shunt made by Alcon to increase the uveoscleral flow of fluid out of the eye. The Cypass is a polyamide device which is flexible. The micro-stent is 6.35 mm long and has a 510 micron external diameter and a 300 micron lumen which is fenestrated with microholes along its length. This allows a circumferential egress of fluid from the stent into the suprachoroidal space.

iStent Supra is a suprachoroidal stent made by Glaukos Corporation designed to increase flow of fluid from the eye through uveoscleral outflow. iStent is a heparin-coated stent which is 4mm in length and a0.16 -0.17 mm lumen made of polyethersulfone and a titanium sleeve. The stent has retention ridges to keep it in place. The iStent Supra can used by itself or during cataract surgery.

The eye is formed with viscoelastic and a gonio lens is placed on the eye to visualize the angle. The iStent Supra is inserted into the suprachoroidal space between the ciliary body and sclera.

The most common complication was bleeding which resolved. The eye pressure reduction was approximately 35%.

The eye is formed with viscoelastic and a gonio lens is placed on the eye to visualize the angle. The iStent Supra is inserted into the suprachoroidal space between the ciliary body and sclera.

The most common complication was bleeding which resolved. The eye pressure reduction was approximately 35%.

Reducing Aqueous Humor Production

ECP is a laser device used to apply laser photocoagulation to the ciliary body to reduce the production of aqueous humor. ECP is cyclodestruction of the ciliary body. Photocoagulation reduces the production of fluid inside the eye and therefore reduces the eye pressure. The ECP probe consists of a laser source, light, and camera. The laser delivers 810 nm wavelength laser light in a continuous energy application.

ECP may be used to treat many types of glaucoma including open-angle glaucoma, congenital glaucoma, and others. The procedure is usually performed during cataract surgery but may be done as a stand-alone procedure. The laser probe is inserted into the anterior chamber and advanced across the eye and behind the iris to the ciliary body. The laser treatment is applied to the ciliary processes until there is whitening of the processes. Approximately 240 degrees or so can be treated through a single incision. If more treatment is needed another incision can be made.

ECP reduced the eye pressure by about 8 mmHg with fewer medications needed to control the eye pressure. The ECP treatment can cause a significant inflammatory response inside the eye and steroid treatment is needed. Other complications include eye pressure spike and hyphema or bleeding.

The Micropulse P3 is somewhat similar to the G-Probe by Iridex except it produces a safer method of treatment to the ciliary body. The MP3 laser device finely controls the laser application to the eye. The laser uses micropulses to perform transscleral cyclophotocoagulation to the ciliary processes. This avoids over heating and burning of any ocular tissue.

On an average, the Trabectome procedure lowers the eye pressure about 30% from the baseline eye pressure. There is some mild bleeding from Schlemm’s canal but this usually resolves within 1 week.

In most cases, the procedure is performed in an out-patient surgery center. The patient is given a short acting anesthesia drug and while they are asleep a numbing medication is used to provide anesthesia for the procedure. The superior and inferior halves are treated in 90 second treatment times. The MP3 probe is placed on the eye just posterior to the limbus (where the clear portion of the eye and white portion meet). The probe is passed along the half of the eye back and forth for 90 seconds. The probe is moved 1 clock hour every 10 seconds. The other half is treated in the same manner.

The eye pressure is reduced by an average of 30 to 40%. This procedure does cause an inflammatory reaction to the laser treatment and is treated with steroids. Some patients do have pain for a short period of time after the procedure.

Probe Position on the Eye

Subconjunctival Filtration

The XEN gel stent is a stent manufactured by Allergan for the treatment of open-angle glaucoma. The stent allows fluid from the anterior chamber to filter under the conjunctiva which covers the white portion of the eye. The XEN stent is made of gelatin and glutaraldehyde. The stent is loaded on a 27-guage needle disposable injector. There are three sizes of the stent based on the size of the lumen which are the XEN 45 (45 micron lumen, 63 micron lumen, 140 micron lumen). Obviously, the larger the lumen is the more fluid is drained from the eye.

The XEN gel stent is indicated for use in patients with open-angle glaucoma, pigmentary glaucoma, and/or pseudoexfoliation glaucoma.

The eye is formed with viscoelastic and a Gonioscopy lens is placed on the eye. The stent is pushed through the sclera ab interno into the subconjunctival space. The fluid that filters through the stent forms a filtering bleb of the conjunctiva where the fluid is absorbed. An antimetabolite such as Mitomycin C may be injected beneath the conjunctiva to keep the bleb functioning.

The XEN 45 reduced the eye pressure by 20% in 75% of patients. Needling of the bleb was needed in about 30% of patients. The larger stents are under study at this time.

The InnFocus Microshunt is made by Santen Inc. for the treatment of open-angle glaucoma. This device is placed ab externo. The device is 8.5mm long and 0.350 mm in diameter with a lumen of 70 microns. It is composed of polystyrene-block-isobutylene-block-styrene. The InnFocus Microshunt may be placed by itself or in conjunction with cataract surgery.

After local anesthesia is obtained, a small conjunctival peritomy or incision is made usually superiorly on the eye. A needle is used to create a tunnel through the sclera into the anterior chamber. The tip of the shunt is then passed into the anterior chamber. The conjunctival incision is closed. Mitomycin C is injected subconjunctivally in the area of the shunt.

Complications include iris-shunt touch, bleeding, incision compromise. The average eye pressure went from 24mmHg to 11 mmHg with the mean number of glaucoma medications reducing from 2.4 to 0.9 medications.

Summary of MIGS

MIGS are a fairly new category of glaucoma treatment procedures which are less invasive than traditional glaucoma surgery with moderate reduction of eye pressure. MIGS are another alternative in the available treatment options for glaucoma. There continues to be a large amount of research into these types of procedures.

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(One of Dr. Croley’s patients wrote the following letter to local news organizations)

Good Afternoon: Thought I’d give you a heads-up for a true community service feature.

James Croley, MD is an eye surgeon located in Cape Coral [Bonita Springs and Lehigh Acres]. He has been serving in Cape Coral for about 30 years and has grown to be world renowned.

Dr. Croley enjoys a reputation, as a result of his professionalism and accomplishments, that serve to set him apart from any other in a delicate field. He’s a giving, feeling individual, dedicated to making better those things that serve to improve the quality of life in our society.

Dr. Croley has now authored a fabulous book entitled “Believing is Seeing.” The book is designed to provide insights into how to improve one’s health and welfare in a complicated world….and does just that!

I believe that a feature focusing on the life and times of this extraordinary man would represent a true community service. In line with the Doctor’s giving persona…proceeds from the book sales will be donated towards Missions.

Happy Easter & God Bless,

Dick

Dr. Croley, Thank you for seeing me as a new patient! You came highly recommended by [a friend] and I found my experience to be not only professional and thorough, but friendly as well! See you in February for a six-month check.

My Best, Kerry

Ps. It was a pleasure meeting your staff as well!”

Kerry

Very professional office, staff and doctor.

Ron

I did not always know why I was doing some procedures but the end result was great and much better than expected.

Zadok

I trust Dr.Croley with my eyes. He is the best eye doctor I have ever been to. He is genuinely concerned about my pressures and being diabetic he keeps track of any changes. I would and have recommended him to my friends. I feel blessed that Dr. Croley is looking after me.

Karen

Trust completely. Do not want to ever have to change doctor.

Barbara

Very pleased and love the entire staff. Will highly recommend Dr. Croley. I have good results.

Beverly

I’m now excited to get the other eye done.

Judith

Dr.Croley and his friendly, efficient staff make my appointments very pleasant. I also appreciate Dr. Croley’s current knowledge of new procedures and possibilities.

Judy

Very nice office, great staff very caring & friendly

Angela

Has many patients but devotes time only for you when with you. Made me feel very much at ease with her compassion and personal interest. Office staff very courteous & definitely trust Dr. Croley.

Mareann

Dr.Croley is well-versed and articulate and maintains state-of-the-art knowledge and technology. No reservations in recommendations.